If you mount a 2X teleconverter does it automatically set your aperture to like f/8? Because if not couldn't I get one and mount it with my 50mm f/1.8 to make it a 100mm(150mm) f/1.8 with a minimum focusing distance of like 10in. would it make a good macro lens?

With every tele-converter the closest distance to the subject remains as with the original lens, only the manification is increased 2x (with a 2x converter that is).
So as your 50mm gets down to approx. 1:8 you'll be able to do 1:4 with a 2x converter - nothing more...
And beware:
1. You need a good converter
2. The optical resolution of every lens is reduced by 2
The latter may no pose a prob if the lens is very good and exceeds the sensor-resolution. But in some cases you may be equally well off to do digital-zooming in with pp.